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We did an addition on our house and installed a two zone heat system with one of the HVAC units in a small room in our unfinished attic. There are insulated ducts in the attic also coming from the room for this system. The problem we are having is that we cannot get the temperature in the attic under about 40 degrees. We have added additional roof venting (both soffit and top of roof) with little effect. We want to get the temperature closer to the outside to prevent ice dams and condensation problems.

The HVAC room is drywalled and has insulation. The ducts are insulated the flexible insulated variety (R-4?). It seems like the only explanation is that there is heat coming from the HVAC room or duct work. Any suggestions?

duct sealing

Use special duct sealing mastic on duct joints. Can use foam or caulk at boots and penetrations. Keep in mind warmair supply leaks outside the thermal envelope cause massive negative pressure inside which can backdraft atmospherically vented appliances. I'd increase that duct insulation. Don't forget other attic bypasses such as around stink pipes, wiring chases, etc. Warning! Chimney clearances cannot be packed with insulation. Fire Hazard. Can and should be properly firestopped such as with sheetmetal and caulk.
HTH

Attic air handler

Originally posted by bwal2

Originally posted by threeboys Thanks, guys for the input.

bwal2 -- alright, why do you say "keep good insurance"??? Don't like Trane or attic installations?

Bwal,
I am getting estimates to replace a one unit, one cold air return on a two story residence with a two unit system. Of the 4 estimates I have had, 3 want to put the air handler in the attic and only one suggests leaving the upstairs air handler on the ground and building a new return duct through the floors next to the existing supply duct.
Are overflowing condensate pans your only resistance to attic units?
Thanks

Nothing wrong with Trane.
No better, no worse than anybody else's.
It's just simple economics.

The condensate pan must actually catch the water in order to do any good.
It is very common to put the furnace in the attic.
It is also very common to pay somebody to repair water damage.
If the unit freezes up, ice could form on the piping between the indoor & outdoor coil.
When that ice melts, it is anyone's guess as to where the water will go.
Also, adequate access must be provided.

Don't let somebody cram this into a corner.

Just be sure you go into this with both eyes wide open.

I haven't seen your house, and don't know your contractor. Just be sure you voice your concerns ahead of time.